The invention resides in a particle filter with carbon deposit or soot combustion for Diesel engines, comprising a filter body having filter areas of sinter metal through which the engine exhaust gas is conducted from the upstream raw gas side to the downstream clean gas side for removing particles from the exhaust gas and electric heaters are arranged at the downstream side for burning off the particle or soot deposits on the sinter metal filter areas.
Particle filters of the above-mentioned type are known from DE 198 10 738 C1. They operate with filter pockets which are closed along their outer circumference and which are stacked on top of one another normal to the pocket plane and in communication with one another in the end areas of their central pocket openings to form a filter body. Raw gas is conducted through the pocket openings centrally into this filter body and hot gases of a burner flow in the direction of the pocket planes between the pockets so that hot gases and fresh gases mix between the pockets and heat the outside of the pocket walls sufficiently for the combustion of carbon deposits thereon.
Particle filters of this type are actually in use and satisfy the functional requirements but, because of their design and the use of a burner, they are expensive and also space-consuming so that their use, particularly in exhaust gas systems of passenger cars, is limited.
In another known particle filter with carbon deposit combustion (EP 0 650 551 B1) a filter body of a sinter metal, on which the carbon or soot is deposited, is electrically heated. For this purpose, a spray electrode is disposed, in the raw gas flow direction, ahead of the filter body, by way of which the particles are charged or, respectively agglomerated and deposited on the filter surfaces mechanically as well as electrostatically since the filter body acts as a collector electrode. For the regeneration of a filter charged in this way, an electric current is from time to time conducted over the filter body, whereby the filter body, acting as a resistance element, is heated to ignition temperature.
There is a multitude of additional particle filters for Diesel engines known, which are electrically heated for the combustion of soot, some in connection with filter bodies which include filter surfaces of sinter material (DE 195 20 146 C1, EP 0 849 444 A2) some with other types of metallic filter bodies (EP 0 837 228 A2) and some with ceramic filter bodies, particularly in the form of honeycomb filter bodies (DE 36 08 801 A1, EP 0 485 974 B1). In some of these filters, the electrical heating in the raw gas inlet area is achieved by resistance wires disposed in the entrance channels with the aim that, after ignition of the soot at the beginning of the channel, the flame front proceeds toward the end of the channel, that is, that the combustion initiated at the raw gas side proceeds following the gas flow toward the clean gas side. In addition to, or independent of, the soot combustion enhanced by the electrical heating, some chemical compounds may be employed which enhance the reaction. Also, motor control means for increasing the temperature of the exhaust gases and engine operating procedures for improving the combustion of the soot may be used.
It is the object of the invention to improve particle filters with carbon or soot combustion for Diesel engines to the point that the advantages which sinter metal filters structures have for particle deposition and the regeneration by combustion of the carbon or soot can be utilized and those filters operate with minimal energy consumption, a high degree of soot combustion and can be manufactured advantageously and economically.